Re: [linux-audio-dev] nice [was: jack, low latency and IO]

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Subject: Re: [linux-audio-dev] nice [was: jack, low latency and IO]
From: Jack O'Quin (joq_AT_io.com)
Date: Sat Dec 11 2004 - 18:33:58 EET


Jens M Andreasen <jens.andreasen_AT_chello.se> writes:

> I have bitched the Mandrake-team for shipping a version/config of jack
> that cannot work. It appears like it might be the jack-team that is (at
> least partially) to blame ... (?)

If you discover a bug in JACK, please open a report...

  http://jackit.sourceforge.net/mantis/

> I said that they (Mandrake) set up jack to have its sockets on /tmp,
> which cannot work when /tmp is part of journaling file-system.

Perhaps they should configure using --with-default-tmpdir=PATH. The
default path, /tmp, is not usually the best choice, but has the major
advantage of being present on every system. For a default, that's
good.

Distribution makers may have reason to know that a better option is
available. Some use /dev/shm, which is needed for POSIX shared memory
support and therefore often configured correctly. Beware, however,
that compiling JACK to use POSIX shared memory will conflict with that
choice.

> After that, I have had a look at various options that are available in a
> clickedeclick style after install. One of them is to empty /tmp on
> reboot.
>
> At first I thought that this option would do
>
> # rm /tmp/*
>
> .. or some such. Apparently not because when i do df:
>
> -------------------------------------------------------
> [jens_AT_elephant jens]$ df
> Filesystem Size Used Avail Use% Mounted on
> /dev/hda5 3,4G 2,2G 1,1G 69% /
> /dev/hda7 4,3G 2,0G 2,3G 47% /home
> none 126M 0 126M 0% /mnt/ramfs
> /dev/hda1 1,6G 1,4G 207M 87% /mnt/windows
> none 126M 68K 126M 1% /tmp
> -------------------------------------------------------
>
> ... , it should be clear that /tmp is now similar to /mnt/ramfs (which
> is the one I created from the guidelines in the jack source-
> distribution.)

A better check is probably something like this...

 $ grep tmp /etc/fstab
/dev/hda8 /tmp ext2 defaults 0 2
none /dev/shm tmpfs defaults 0 0
jack /tmp/jack tmpfs defaults 0 0

You want it to say `tmpfs' (or maybe `ramfs').

> [jens_AT_elephant jens]$ /usr/bin/jackd --version
> jackd version 0.98.1
> default tmp directory: /tmp
>
> ... and:
>
> [jens_AT_elephant jens]$ /usr/local/bin/jackd --version
> jackd version 0.99.0 tmpdir /mnt/ramfs protocol 13
>
> ... , then I get the impression that something very positive happened
> between jackd_0.98.1 and jackd_0.99.0
>
> Comments?

Mixing two different versions of JACK on the same system is usually a
disaster. Programs linked with /usr/lib/libjack.so.0 will generally
not work correctly with /usr/local/bin/jackd.

-- 
  joq


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